1. Field of the Invention
The present invention relates to a microplate liquid handling system and, more particularly, to a microplate liquid handling system for simultaneously delivering liquid reagent, liquid specimen, etc. to a plurality of desired wells for specimen/reagent reaction arranged in a microplate in n×m matrix.
2. Description of the Related Art
A microplate liquid handling system has conventionally been known which is used to deliver reagent, specimen, etc. to desired ones of a plurality of wells formed in a microplate. The microplate liquid handling system has a dispensing mechanism and a moving mechanism, and the dispensing mechanism is equipped with a cylinder having a nozzle. Mounted to the nozzle is a dispensing tip, through which liquid can be sucked and discharged. The cylinder is equipped with a plunger for sucking liquid into the dispensing tip mounted to the nozzle and for discharging liquid from the interior of the dispensing tip.
As disclosed, for example, in JP 8-271528 A and JP 5-232124 A, the moving mechanism is capable of moving the nozzle to an appropriate position above a desired well in the microplate, and the dispensing mechanism can be moved in the lateral, longitudinal, and vertical directions (the X-, Y-, and Z-axis directions) above the microplate. Generally speaking, arranged in the microplate are 96 wells in 12×8 matrix, and so-called dispensing is conducted, that is, reagent or specimen is delivered to a desired well from a dispensing tip mounted to the nozzle of the cylinder of the dispensing mechanism, so that reagent-specimen reaction or the like is effected in the well.
There are four types of microplate liquid handling system: 12-gang type, 8-gang type, single-gang type, and 96-gang type. In a 12-gang type microplate liquid handling system, the nozzles of twelve cylinders arranged in parallel and in a straight line in the longitudinal direction of the microplate are operated in synchronism with each other, and it is possible to perform suction or discharge of liquid such as reagent collectively on the dispensing tips mounted to the twelve nozzles. For example, it is possible to simultaneously discharge reagent onto each of the specimens in the plurality of wells arranged longitudinally in a row in the microplate. 
Similarly, in an 8-gang type microplate liquid handling system, eight nozzles arranged in parallel and in a straight line in the lateral direction of the microplate are operated in synchronism with each other, and it is possible to perform suction or discharge of liquid such as reagent collectively on the dispensing tips mounted to the eight nozzles. In a 96-gang type microplate liquid handling system, 96 nozzles arranged in 12×8 matrix are operated in synchronism with each other, and it is possible to perform suction or discharge of liquid such as reagent collectively on the dispensing tips mounted to the 96 nozzles and to discharge reagent or the like simultaneously onto all the 96 wells in the microplate. In a single-gang type microplate liquid handling system, a single nozzle is solely operated.
For example, regarding enzyme reaction tests, such as drug metabolic reaction tests, there are a number of kinds of test using a microplate with wells arranged in a n×m in matrix. In these testing, m kinds of samples are poured into all the longitudinally arranged wells and n kinds of enzyme reagents are poured into all the laterally arranged wells to collectively effect n×m enzyme reactions.
To perform dispensing row by row both longitudinally and laterally, the conventional 96-gang type microplate liquid handling system, in which 96 nozzles collectively perform ganged operation, solely requires attachment of dispensing tips to a certain row of the 96 nozzles. However, a tip container must require an area n-times or m-times as large as the requisite area for containing the 96 tips. That is, a large installation place is required. Further, a critical error may occur in the test results due to attachment of the row of dispensing tips to an erroneous row of the nozzles. Further, the reagent vessel for containing sample and reagent also has to exhibit a similar largeness. This requires a large amount of sample or reagent, which is valuable in itself, resulting in a marked deterioration in test efficiency.
In the case of a n- or m-gang type microplate liquid handling system fixed in terms of direction, n or m nozzles collectively perform ganged operation, so that it is possible to collectively dispense sample or reagent in the arrangement direction of the microplate liquid handling system with a microplate in which the wells are arranged in matrix. However, in a direction perpendicular thereto, dispensing has to be performed with a single dispensing tip attached to a certain one of the n or m nozzles, as in the case of the 96-gang type microplate liquid handling system, so that it takes long time to complete dispensing, resulting in a deterioration in test efficiency.